As well known in the art, an automatic transmission automatically shifts speeds on the basis of a vehicle driving state and operation of a driver. Such an automatic transmission includes a plurality of frictional elements, such as clutches and brakes, such that multi-speed shifting is realized by hydraulically controlling them.
Throughout the present specification, including the claims, a frictional element that becomes engaged during a shifting is called an on-coming element, and a frictional element that becomes disengaged during a shifting is called an off-going element. In addition, a hydraulic pressure duty rate applied to the on-coming element is called an on-coming pressure duty, and a hydraulic pressure duty rate applied to the off-going element is called an off-going pressure duty.
According to the prior art, when a 4 to 3 downshift condition is satisfied during an execution of a 3 to 4 upshift, e.g., due to an accelerator pedal operation of a driver, a required 4 to 3 downshift is started only after a currently proceeding 3 to 4 upshift is fully finished.
Therefore, according to such a prior art, when a driving condition of a vehicle is rapidly changed such as in the case in which a driver quickly changes an operation of an accelerator pedal, such a request of a driver is not promptly achieved by prompt shifting. That is, responsiveness in shifting does not adequately react to a request of a driver.
Typically, a more prompt achievement of a request of a driver is expected during a 4 to 3 downshift to a 3 to 4 upshifting is requested.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms part of the prior art that is already known in this country to a person of ordinary skill in the art.